


Sleep tight

by WednesdayLeaf



Category: Undertale (Video Game)
Genre: Alternate Universe - Underswap, Drug Use, Drug-Induced Sex, M/M, Non-Consensual Somnophilia, Plot What Plot/Porn Without Plot, Rape/Non-con Elements, Shameless Smut, Sibling Incest, Somnophilia, This be messed up, noncon
Language: English
Status: Completed
Published: 2017-05-02
Updated: 2017-05-02
Packaged: 2018-10-26 22:11:30
Rating: Explicit
Warnings: Rape/Non-Con
Chapters: 1
Words: 3,117
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10795764
Author URL: https://archiveofourown.org/users/WednesdayLeaf/pseuds/WednesdayLeaf
Summary: Swap!Papyrus drugs his brother to make sure he stays asleep, then has his way with him. That's it. That's the story.





	Sleep tight

**Author's Note:**

> I've never actually written smut outside of RPs before, so this was pretty much a self-challenge, especially the non-con part. I'm well aware of how messed up it is, but hey if it's not your dealio, that's what the tags are for. As a quick reminder:
> 
> THIS CONTAINS NON-CON/RAPE, SOMNOPHILIA AND INCEST. PLEASE AVOID IF ANY OF THIS COULD UPSET YOU.

Papyrus knew that this was wrong. He knew that he was seriously fucked up to even be _considering_ this, but despite the self-disgust churning in his gut, he found himself moving towards the edge of Sans’ bed and staring down at his younger brother.

Sans was splayed across his bed, limbs askew and mouth open slightly as he took slow breaths. It was clear he was deeply asleep, not even reacting when Papyrus pulled back the covers and knelt down beside him. The stuff Muffet had given him – for a steep price - really had worked.

He sucked in a breath at the way Sans’ shirt had been tugged up in his sleep, baring the curve of his pelvis and his lower spine. His pupils shifted to Sans’ face, slack in unconsciousness and just as sweet as it was when he was awake, though it lacked his usual exuberance. Yet his innocence was still there, clear as day.

For a moment, Papyrus warred with himself. This wasn’t some impulsive decision – he’d been dealing with these urges for a long while now, the horror gradually fading each time he touched himself with Sans’ face and body on his mind. But it wasn’t enough now to just imagine what it would feel like, to have his brother under him, to feel his body shiver and the soft moans he imagined Sans would make. He _needed_ more. He would never dare to risk driving Sans away from him by revealing how he felt, but he…he could have this. He cared for Sans, he protected him and supported him, he was a good brother – he could _have_ this.

Mind made up, he gave in and gently tugged off Sans’ shirt all the way, slipping his arms through the holes just like when he was a kid. Sans’ head lolled back against the pillow, his body completely limp, sending a jolt of arousal to Papyrus’ groin.

“Sans..?” He murmured, wanting to check that Sans really wasn’t going to wake before he went any further. His brother didn’t even shift in his sleep. He repeated the other’s name, louder this time, with the same lack of response.

A moment later he was straddling him, simply sitting on Sans’ smaller pelvis and feeling his breathing pick up at how good it felt. He was finally doing this – finally able to feel the real thing. He impulsively ground down against him, and even with two layers of clothing in the way he couldn’t help but groan at the delicious friction.

His gaze darted to Sans’ face again, sighing shakily. Still no response. He leaned down, bracing himself on one hand whilst the other cupped Sans’ cheek. He’d turned the light on when he came in, wanting to be able to see every moment of this in perfect detail – a video camera set a couple feet away to capture the act in case his memory failed him. He didn’t know if he’d even be able to do this again, so he wanted to make the most of it.

He chuckled faintly, the sound self-deprecating. “Look what you’ve done to me, Sans…I really am trash.” His brother offered no reply, no assurances or affectionate hug. He simply breathed slowly, mind lost in a drug-induced sleep and mouth still slightly open. He really was so cute…and even cuter now, with the knowledge that Papyrus could finally live out his fantasies. At least, some of them – he didn’t want to cause anything too permanent or suspicious. 

With another sigh, he pressed a kiss to Sans’ mouth, enjoying the soft pressure before sliding his tongue into the warm wetness of his brother’s mouth. He muffled a groan and quickly deepened the kiss, tongue curling almost frantically around Sans’ as he shivered at the taste, eye sockets closing to better appreciate the sensation. This was what Sans tasted like, felt like, and even if Sans wasn’t responding to the kiss he could still memorise how this felt and use it to fuel his imagination later.

Sans made a faint sound and he froze, realising he’d been grinding against him again, his erection straining against his shorts. His gaze snapped to Sans’ face but to his relief his brother was still asleep. He leaned back a little from the kiss, a cord of saliva connecting them for a brief moment, and he offered him his typical lazy smile.

“Sorry Sans…Got carried away…” He nuzzled into his neck, breathing in his scent with a blissed sigh. This was so much better than stealing one of Sans’ pillows or shirts…His tongue darted out to lick over Sans’ neck, meticulously exploring each of his vertebrae and smiling in delight when he felt his brother’s body shiver beneath him. “You like that?”

He kept licking whilst his hand slid from Sans’ cheek down to his hip, thumb rubbing gently against the curve before reaching under him to push Sans’ pelvis up against his own, enjoying the warm pressure against his member. It would be embarrassing that he was already so hard if this wasn’t _Sans._ Sans was…special. He was so innocent and naïve that he doubted his brother had ever even thought about sex, never mind tried it for himself. And if Papyrus had any say in it, no one except him would ever touch Sans like this.

Soft, sleepy sighs and huffs had begun to escape the small skeleton, and when Papyrus tilted his head a little he could see the blue that was tinting his cheeks, as well as his furrowed brow. He wondered how Sans would react if he woke up at that moment. He’d be so confused at first, then…panic and disgust would be his next most likely responses. Papyrus wasn’t so far gone to convince himself that Sans would want this. But…that didn’t mean it couldn’t feel good, even if the focus was on his own pleasure here.

He set Sans’ pelvis back down on the bed and pulled off his own hoodie, throwing it on top of Sans’ shirt before turning his attention back to his half-naked brother. Sitting on top of him like this, he noticed the difference in their sizes now more than ever, his own body dwarfing Sans’. It gave him an undeniable thrill, making it hard for him to stop himself from humping him again. But he kept himself in check. This time, he wasn’t just going to be fucking against his own hand or Sans’ shirt, and he knew it’d feel even better the harder he was.

“You’re gorgeous, Sans,” he murmured, trailing kisses down the other’s sternum, his fingers exploring his ribs one by one. Sans’ body shifted a little under his but not enough to make him check to see if he was waking up, confident by now that Muffet’s drink would work. “See you every day…Training, going on your patrols, cooking, doing puzzles…Fuck, it’s been so hard not to touch you like I want to…Especially when you get so close to me all the time…”

Every innocent hug left him half-hard and aching, wishing that Sans would stay pressed up against him for longer even as he felt his self-restraint slowly snapping. At least he’d kept himself from taking Sans when he was awake and aware of what was happening – he’d never want to make his brother cry.

He ducked lower, orange tongue sliding over Sans’ iliac crest and leaving a faint trail of saliva. He pulled the other’s shorts off in a quick movement, looking over his pelvis hungrily before returning to licking the smooth bone. Sans made more of those arousing sounds, and he paused when he noticed the soft blue of the other’s magic gathering in his pelvis.

He swallowed, then started to gently knead Sans’ lower spine, hand easily enclosing it entirely. “That’s it…Good boy…” His pupils were riveted to the pussy gradually being formed, feeling the slight wetness of pre-cum in his pants at the sight of it. “Fuck, Sans…”

Mouth pressed to the slit, the first thing he noticed was how warm it was. He hiked Sans’ legs over his shoulders for a more comfortable position and licked against the magic, groaning at the delicious taste and the way Sans shuddered. A moan left his brother when he pressed his tongue inside, his hands tightening on Sans’ hips as the sound went straight to his dick. He wanted to take more time to taste Sans and prep him for this, but he couldn’t wait any longer.

He dropped Sans back onto the bed and removed his own shorts in quick, hurried movements, unable to look away from his naked and aroused brother. His imagination didn’t live up to the reality of seeing Sans with his legs spread and face flushed, that small, perfect pussy looking so inviting. He crawled back over his sleeping form, spreading his legs wider and pushing them up slightly so that they neatly bracketed his own hips, painfully hard yet wanting to savour every moment as he lined up his member with the blue magic.

He moaned his brother’s name as he slowly sank into him, grasping his hips to keep them in place. He’d barely pressed past the head of his cock and already he could feel the small vagina straining to take him in, Sans making odd, gasping noises the further he pushed. But he couldn’t stop now, not when he was so close to achieving something he’d been fantasizing about for ages and might never have the chance to do again.

Sweat beaded on his forehead whilst he forced himself further in, watching his cock sheath itself in his brother. Sans was so warm and wet, pressing against his dick in a way that left him panting lustfully with a blush dusting his cheeks. He froze when Sans cried out, looking to his face as fear lanced through him – but Sans’ eye sockets were still closed, even as his breathing was noticeably quicker and his fingers had grasped onto the bedsheets.

Right. This…This must be hurting him, even when he was unconscious. “Sorry, bro…” He could stop. He could slow down. But the aching in his dick was too painful for him to consider either option. Instead, he leaned forwards so that his chest was pressed flush to Sans’, one arm taking his own weight again and he started to rock against Sans, frowning as he drew back a little only to groan in satisfaction as he sank back into that wet heat.

“Y-You’re so good, Sans…Such a nice pussy, a-all for me…Ah…All for your big bro…” He was barely aware of his aroused mutters, gaze half-lidded as he kept up the slow grinding motion. He could feel himself press in a little more each time, Sans’ magic inevitably giving way to his hard shaft. It was getting easier to sink further in as Sans became wetter and more aroused, his younger brother’s face scrunched up in an adorable way.

“N-Ngh…” Fuck, but this felt so much better than any sex he’d ever had, and he was only half-way in! He’d imagined this moment more times than he could count, but nothing lived up to the reality – the soft yet insistent press of Sans’ walls against him, the hint of lust in his brother’s innocent face, how small and helpless he was beneath Papyrus’ larger frame; it was incredible, and even if this made him the shittiest brother to ever exist, he didn’t give a damn.

Not wanting to cum when he wasn’t even fully inside Sans, he moved both hands to his brother’s hips and thrust more insistently, letting his weight rest on the other skeleton. Sans was sturdy enough to handle it, and it was worth it to feel his insides be forcefully stretched by his large dick, the feeling especially noticeable as he felt the entrance press tight against his base. His moans mixed with the sounds Sans gave, though whether they were pained or in pleasure he was past the point of paying attention.

He moved in earnest now, hips jerking in frantic movements as his lust overtook him. All he could think about was the feeling of Sans’ body under him, how his insides gave in to Papyrus’ thrusts but remained so damn tight around him, like Sans didn’t want to let him go. He buried his face in his brother’s neck and whined as his vision was overtaken by a burst of white, body shaking with the force of his climax.

Slowly, he came back to himself, registered the way he was slumped over Sans and panting heavily against his vertebrae. Then he noticed how much wetter Sans’ pussy was and realised he’d cum inside him. Something between a groan and a sigh left him, his dick pulsing a little. He’d fucked his brother…He’d taken his virginity all for himself, and coated his insides with his cum…Probably his thighs and pelvis too, with the way he could feel the hot liquid leaking out…He shivered, arms wrapping around Sans, content to simply lay there as he tried to recover his breath.

“Sans…” he muttered, fingers stroking over the smaller skeleton’s spine and feeling the shudders that occasionally wracked his frame. He tilted his head so he could see his face, noting that it was the same as earlier, though the blue blush was deeper now. “Heh…” He cupped Sans’ cheek again, stroking it softly before drawing him into a kiss.

This time he wasn’t in a rush, coating the other’s teeth in a thin layer of saliva before pressing into his mouth, Sans’ jaw dropping unresistingly. His hand moved to cup the back of his neck to mimic the feeling of Sans responding to the kiss, even if his tongue barely moved as he twisted his own around it and sucked. He hadn’t done as much kissing as he had fucking, but even unconscious he’d definitely rate Sans as being one of the best kisses he’d had. Just showed how amazing Sans was.

Feeling himself start to harden again, he broke the kiss and chuckled, looking down at Sans affectionately. “I really can’t get enough of you.”

He reluctantly drew out of Sans, moving onto his knees so that he could see the mess he’d made of Sans’ pelvis. The sight made him smile. Sans’ magic was see-through enough that he could see the orange cum pooled inside him, more of it leaking out over his thighs, staining the white bones. He rubbed his thumbs against the insides of Sans’ femurs as if he could make the cum stick there forever, delighting in the pleased hums that left his brother. “You look amazing, bro.” He’d love to fuck him again, to fill his pussy up again and again until his brother wouldn’t be able to walk in the morning – but he didn’t want to make Sans too suspicious. With any luck, Sans would have no idea what had happened, and Papyrus would get the chance to do this again.

A flicker of aching arousal in his cock reminded him that he wasn’t done for tonight. Breathing starting to pick up again in his eagerness, he moved Sans’s legs so that they were pressed together and he was straddling them before pulling his brother’s body down impatiently until his knees were on either side of Sans’ shoulders. The smaller skeleton’s mouth was still open from their earlier kissing, and he didn’t even have to touch his cock for it to be completely erect.

This was one of his older fantasies, alongside actually fucking Sans, and kissing him had given him a good idea of what it’d feel like. “You ready, Sans?” Sans’s eye sockets remained shut, body more relaxed now.

He tilted his hips until his dick brushed against Sans’ mouth, and it only took that slight jolt for him to give in and lower himself into Sans. For a moment he worried that his shaft would be too big for Sans’ mouth, but despite the faint choking noise Sans made he slid in just fine.

“A-Ahh…Fuck…” Sans’ mouth was just as hot and wet as his pussy, but the unconscious movements of his tongue against his dick added a new stimulation that left him grabbing onto the sheets. There wasn’t any coordination or skill to it, not like with any blow jobs he’d had in the past, but all it took was one glance down at his dick sunk into Sans’ mouth for pleasure to jolt up his spine. Soon he was rocking into the slick warmth, hunched over as he tried to find the point that best let him press into Sans’ throat.

After a few experimental thrusts, he grabbed the back of Sans’ head and pulled him onto his cock, grunting in arousal. If Sans couldn’t move he’d just take care of it himself, mindlessly fucking his brother’s mouth, enjoying the way he felt him tremble slightly under him. “M-Mgh…Ah…So good…” He pressed Sans’ mouth flush to his own pelvis and rocked harshly against his tongue and throat, the chocked-off noises and unconscious jolts only heightening his pleasure until he finally came with a stuttered moan.

He kept Sans held in place as cum filled his mouth, determined to watch whilst Sans gave a muffled cough before swallowing instinctively to clear the blockage, shuddering at the way it caused his throat to convulse around his softening cock. The sight was almost enough to get him aroused again, but he held himself in check, his lingering satisfaction helping in that regard.

Smiling tiredly, he stroked Sans’ skull. “You took my dick so well, Sans…I’m proud of you…Heh, if you offered to do this for me, I’d have no problem with staying awake at my post.”

He moved out of the other’s mouth with a stifled groan, wishing he could stay in there for longer. The sight of his cum leaking out of Sans’ mouth appeased him a little, and he smiled in satisfaction as he shifted off of Sans. Glancing towards the camera, he paused before gathering Sans up in his arms, turning towards it and settling Sans in his lap. It took a little maneuvering, but soon he had Sans facing the camera with his legs held wide, slumped back against Papyrus’ chest – giving a great view of what he’d done to his brother. That’d be something to get him going later.

He grasped Sans’ chin and pressed a soft kiss to his forehead, thumb gently wiping some cum back into his mouth. “Let’s get you cleaned up, yeah?”

 

**Author's Note:**

> Comments and kudos are really appreciated! Feedback would be awesome since I'd like to improve, plus I'm up for taking suggestions.


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